Mechanism to control the torque delivered by impact wrenches



2 Sheets-Sheet 1 INVENTORS 0L THE TORQUE C. H. ELLIOTT ETAL MECHANISM TO CONTR DELIVERED BY IMPACT WRENCHES Hm y mm M Na 5 m T 2A J M M m Z CR 5 N Jan. 30, 1962 Filed Sept. 17, less Jan. 30, 1962 c. H. ELLIOTT ETAL 3,018,866

MECHANISM TO CONTROL THE TORQUE DELIVERED BY IMPACT WRENCHES Filed Sept. 17, 1958 2 Sheets-Sheet 2 if 43 INVENTORJ .5) j; ATTORNEY United States Patent 3,018,866 MECHANISM TO CONTROL THE TORQUE DELIVERED BY lit PACT WRENCHES Charles H. Elliott and Richard E. Eckman, Houston,

Tex., assignors to Reed Roller Bit Company, Houston,

Tex., a corporation of Texas Filed Sept. 17, 1958, Ser. No. 761,627 3 Claims. (Cl. 192-150) This invention relates broadly to fluid actuated rotary impact wrenches used for rotatively impacting threaded elements such as screws, nuts, bolts and the like, but more particularly to a torque controlling device for such wrenches. j I

One object of this invention is to provide a fluid actuated rotary impact tool with simple and eflioient means adapted to automatically shut off the pressure fluid supply to the tool upon a predetermined torque output of the tool.

Another object of this invention is to provide such a tool with an improved throttle valve mechanism adapted to shut off automatically and prevent further operation of the tool when its torque output has reached a predetermined maximum, thereby eliminating delivery of unnecessary impacts, reducing operating time and use of operating fluid as Well as assuring uniformed and controlled tightening of the threaded elements.

Another object of this invention is to provide such a tool with simple and dependable means for adjusting, within a relatively large range up to the maximum torque output of the tool.

Other objects and advantages more or less ancillary to the foregoing reside in the specific construction and aggrouprnent of the elements peculiar to this structure, as

will become apparent from a more complete examination of this specification.

in the drawings:

' FIG. 1 is a side elevational View, partly in section, of a fluid actuated rotary impact tool embodying the invention.

FIG. 2 is a fragmentary view, partly in section, of the tool shown in FIG. 1.

FIGS. 3 and 4 are fragmentary views, in section, of the flywheel mechanism shown in FIG. 1, but with some of the parts in different positions.

FIG. 5 is a view corresponding to a portion of FIG. 2, but with some of the parts shown in different positions.

Referring to the drawings in which like symbols designate corresponding parts throughout the several views, represents generally a fluid actuated rotary motor which includes a cylinder housing 1.1, a stator 12 having a rotor 13 operatively mounted therein and carrying the usual radially movable vanes 14. To one end of the cylinder housing 11 is fastened, by any suitable means, a flywheel housing 16 terminated by a removable cap 17 fastened to the housing by screws 18. To the other end of the cylinder housing 11 is similarly fastened a front housing 19 within which is adequately mounted a rotary impact driving mechanism, not shown, driven by the motor 10 and adapted to transmit rotation and rotary impacts to a work driving shaft 2t). Since the motor 10 and impact driving mechanism form no part of this invention, no further showing or description thereof is thought necessary, other than pointing out that both ends of the stator 12 are closed by end plates 21, one of which is shown in FIG. 1. Through this one end plate extends one end portion of the rotor or drive spindle 22 which is preferably made an integral part of the rotor 13 and is journalled within a ball bearing 24 mounted within the end plate 21. The other end, not shown, of the rotor spindle is also journalled within a ball bearing mounted Within the other end plate located Within the Patented Jan. 36, 1%62 "ice left end, in FIG. 1, of the cylinder housing 11. Adjacent the bearing 24, the drive spindle 22 has mounted thereon for rotation therewith a disc 25, which is rotationally and axially locked by a key 26. Adjacent the disc 25, is a flywheel 27 in the form of a second disc mounted on the spindle 22 for rotation relative thereto. This flywheel is provided with a plurality of equally spaced apertures 28 extending vertically therethrough and each having a ball 29 freely mounted therein. The balls are larger than the thickness of the flywheel, thereby enabling the balls to protrude beyond both sides thereof. The face of the disc 25 adjacent the flywheel 27 is provided with equally spaced V-shaped grooves 30 which extend radially thereof and of a number equal to that of the balls 29. The portions of the balls 29 which protrude from the side of the flywheel adjacent the disc 25 are normally closely fitted within the grooves 30 as clearly shown in FIG. 3, and are normally retained therein by a ball retm'ning plate 31 freely mounted on the rotor spindle 22 for rotary and axial motion relative thereto. The balls 29 always protrude from the side of the flywheel adjacent the retaining plate 31 even when located within the grooves 30, and consequently are always subjected to the axial thrust of the plate 31, which thrust is generated by a compression spring 32. This spring has one end seated against a spring follower 33 freely mounted on the spindle 22, which follower transmits axial thrust to the ball retainer 31 through a needle bearing 34- interposed between the retainer and follower. The other end of the spring 32 'is seated against a second spring follower 35 which has a screw threaded connection with a screw member 36 mounted within the housing 16. Both followers 33 and 35 are rotationally locked to the housing 16 by a tong 37 slidably fitted within a longitudinal groove 38, while the screw member 36 is provided with a polygonal socket 39. After removal of the cap 17, a wrench or the like can be inserted into the socket 39 to turn the screw member 36 and move the spring follower 35 axially to adjust the compression of the spring 32.

Extending laterally from the cylinder housing 11 and preferably made integrally therewith, is a handle 40 into which is screwed a bushing 41. This bushing has a bore d2 extending therethrough and provided with a valve seat 43 engageable by a ball valve 44, which is urged toward the seat 43 by a compression spring 45 interposed between the valve and the inner end of a pressure fluid connector 46 screwed into the outer end of the bushing 41. Beyond the seat 43, the bore 42 is reduced in diameter and connected with a pressure fluid inlet passageway 47 through radial ports 48. From handle 40, the passageway 47 extends to the motor 10' to supply motive fluid to the rotor 13 in a manner well known in this art. A valve operating rod 49 extends from the valve 44 through the inner end of the bushing 41 into a handle cavity 50 where it engages one end 61 of a bell-crank lever 51 pivotally mounted on a cross pin 52. The other end 62 of the lever 5-1 engages one end of a plunger 53 slidably mounted within a trigger member or valve operator 54, which has one end portion extending from the handle and adequately shaped to fit the operators finger. The valve operator 54 is slidably mounted within a handle bore 55 and is rotationally locked thereto by a cross pin 56 engaging a flat portion 57, its slidable movement being limited by either ends of the flat portion engaging the cross pin. The plunger 53 is rotationally locked to the trigger 54 by a cross pin and slot connection Sit-$9, which connection also limits the slidable movement of the plunger with respect to the trigger member. A compression spring 6t} maintains the plunger 53 in engagement with the end 62 of the lever 51. The end of the plunger 53 which extends into the cavity 50, is provided with a slot 63 within which is pivotally mounted by a cross pin 64 a sear lever 65. On the right side of the pivot 64 in FIG. 1, the sear extends over the end 62 of the lever 51, while on the right side of that pivot the sear is provided with a notch 66 normally engaging the end of the trigger member 54. The proportions of the slot 63 and sear 65 permit, under certain conditions of operation, the withdrawal of the notch 66 into the slot 63 and the inward movement of the plunger 53 into the trigger member 54.

In the position of the parts shown in FIG. 1, the sear 6S opposite the end 62 of the lever 51 is also engaged by one end of a trip rod 67 slidable within the handle 40, while its other end engages the inclined or cammed end of a second trip rod 68 which extends into a recess 69 formed Within the flywheel housing 16. The other end of this second rod engages one arm of a lever 70 pivotally mounted within the recess 69, while its other arm is engageable by the spring follower 33. A compression spring 71 maintains the lever 70 in engagement with the second trip rod 68.

Assuming that pressure fluid is admitted to the valve 44 through the connection 46, as the operator depresses the trigger member 54, the notch 66 of the sear 65 which engages the end of the trigger member transmits inward motion to the plunger 53 through the cross pin 64, thereby causing clockwise pivotal movement of the lever 51 and the opening of the valve 44 with respect to its seat 43, thus admitting pressure fluid to actuatethe motor 10 through the ports 48 and passageway 47. During this inward movement of the plunger 53, the sear 65 slides across the end of the first trip rod 67 to assume the posi tion shown in FIG. 2. I

As usual in impact wrenches, the continuous rotation of the motor 10 is transmitted to the drive shaft 20 through the impact mechanism within the housing 19. When free running of the work, such as a nut or the like is completed, seating resistance increases sufficiently to cause the impact mechanism to deliver rotary impacts in rapid successtion to the drive shaft 20. Since many of the impact mechanisms known in this art can be used within the housing 19, no description thereof is necessary other than pointing out that all impact mechanisms are primarily activated by the rotor 13 of the motor 10. In mechanisms of this nature, the foot pounds blow or impact delivered by the impacting member or hammer is directly proportional to the inertia absorbed by the deceleration, upon impact, of the moving parts of the mechanism, which parts include the hammer (not shown) and the rotor spindle 22 to which the hammer is connected. As the work is gradually tightened, the intermittent deceleration of the spindle 22 which takes place upon each impact delivered to the shaft 20, gradually increases in intensity, until the resulting inertia of the flywheel is sufficient to effect release of the flywheel from the spindle.

In the present construction, since the flywheel 27 is normally connected to the rotor spindle 22 through the balls 29 retained into the V-shaped grooves 30 of the disc 25, it will be understood that the inertia of the flywheel is directly proportional to the inertia of the rotor spindle 22. Under certain conditions of operation, the flywheel 127 is free to rotate relative to the rotor spindle 22, but before it can be released from the spindle, the flywheel through its carrying balls 29 must first climb the cams or inclined walls of the V-shaped grooves 30, thereby imparting axial movement of the flywheel toward the right in FIG. 1 to further compress the spring 32. Since the inclines of the cams or of the walls of the grooves 30 is constant, and since the tension of the spring 32 is also substantially constant, it can be deducted that the resulting axial travel of the flywheel is directly proportional to the inertia absorbed by the deceleration of the rotor spindle during each impact of the tool, thereby resulting in the axial travel of the flywheel being directly proportional to the torque delivered by the tool. 7

As hereinafter explained in detail, the axial movement of the flywheel is intended to trip the sear mechanism and shut off supply of pressure fluid to the tool. Since as above stated, the axial movement of the flywheel is directly proportional to the torque delivered by the tool when both the incline of the cams 30 and tension of the spring 32 are constant, it will be understood that by varying the tension of the spring 32 which opposes this axial movement, the amount of inertia of the flywheel resulting in its axial movement, can be varied accordingly. Thus the amount of torque delivered by the tool required to trip the sear mechanism and shut off supply of pressure fluid to the tool, can also be varied.

As the inertia of the flywheel 27 reaches a certain maximum, the balls 29 carried by the flywheel are caused to climb the cams or inclined side walls of the V-shaped grooves 30, thereby effecting the axial movement of the flywheel or more particularly of its component ball retainer 31 toward the right in FIG. 1. This axial movement is transmitted to the spring follower 33 to effect clockwise pivotal movement of the lever 70 and move the rod 68 toward the left and the movement of the rod 67 toward the sear 65. Since this last rod engages the sear adjacent the notch 66 as shown in FIG. 2, it imparts counterclockwise pivotal movement to the sear, to release the notch 66 from the inner end of the trigger member 54, thereby enabling the bell-crank lever 51 driven by the valve spring 45 to move the plunger 53 inwardly against the spring 60, and thereby causing the valve 44 to close by engaging its seat 43. It will be noticed that the closing of the valve 44 and consequently the shutting oil? of the pressure fluid to the tool is effected even though the trig ger member 54 is still depressed by the operator.

As the tool is removed from the Work and the operator releases the trigger 54, the compression spring 32 returns the follower 33 and retainer 31 to the FIG. 1 position, thereby causing re-engagement of the balls 29 with the grooves 30, and the release of the lever 70 from the follower 33. As the operator releases the trigger 54, it moves to the left to the FIG. 1 position, thereby enabling clockwise pivotal movement of the sear imparted thereto by force of the spring 71 acting on the lever and rods 68 and 67, to once more cause the notch 66 to engage the inner end of the trigger 54.

When it is desired to change the torque output of the tool, the cap 17 can be removed and the screw member 36 rotated to vary the tension of the spring 32, thereby increasing or decreasing the required inertia of the flywheel 27 to effect its axial movement.

From the foregoing description it will be understood that the tool is equipped with a simple and eflicient device adapted to automatically shut off the pressure fluid supply to the motor under certain conditions of operation. It will also be understood that the operation of this device is responsive to a predetermined inertia of the flywheel when the drive spindle 22 decelerates upon impacts delivered to the shaft 20, which spindle upon impacts delivered to the shaft 20 is subjected to intermittent deceleration of gradually increasing intensity. In other words, the inertia of the flywheel is directly proportional to the deceleration of the spindle 22, thus it may be stated that the flywheel inertia required to efiect its release from the spindle depends upon deceleration of a predetermined intensity of the spindle.

Although the foregoing description is necessarily of a detailed character in order to completely set forth the invention, it is to be understood that the specific terminology is not intended to be restrictive or confining, and it is to be further understood that various re-arrangement of parts and modifications of structural detail may be resorted to without departing from the scope or spirit of the invention as claimed.

We claim:

1. In a pressure fluid actuated tool for running and impacting a threaded element, the combination of a fluid actuated motor including a drive spindle subjected tosudden deceleration under certain conditions of operation, a passageway conveying motive fluid to the motor to actuate same, a valve controlling said passageway, a spring normally ur-ging and maintaining said valve closed relative to said passageway, an operator for said valve movable relative thereto in valve open or closed positions an operating connection between said operator and valve to open the valve upon movement of said operator to said valve open position, said connection capable of release to enable said valve to close by virtue of said spring even though said operator is in said valve open position, a flywheel on said spindle rotatable relative thereto, a first disc on one side of said flywheel fixed on said spindle, a second disc on the other side of said flywheel axially movable on said spindle, cam means between said first disc and flywheel operatively associated with said second disc to impart axial movement thereto in one direction by virtue of a predetermined inertia of said flywheel upon said deceleration of said spindle and means responsive to the axial movement of said second disc in said one direction automatically effecting the release of said connection.

2. In a tool for rotatively impacting a threaded element, the combination of a fluid motor including a drive spindle subjected to sudden deceleration under certain conditions of operation, a flywheel on said spindle rotatable relative thereto, a first disc on one side of said flywheel fixed on said spindle, a second disc on the other side of said flywheel axially movable on said spindle, cam means between said first disc and flywheel operatively associated with said second disc to impart axial movement thereto in one direction by virtue of a predetermined inertia of said flywheel upon said deceleration of said spindle, a valve controlling the supply of motive fluid to said motor, a spring normally urging and maintaining said valve in closed position, an operator for said valve movable relative thereto in valve open or closed positions, an operating connection between said operator and valve to open the valve upon movement of said operator to said valve open position, said operating connection including a pivotally mounted member actuated by said operator, said connection capable of release to enable said valve to close by virtue of said spring even though said operator is in said valve open position, and means responsive to the axial movement of said second disc in said one direction to close said valve and interrupt said supply of motive fluid.

3. In a tool for rotatively impacting a threaded element, the combination of a fluid motor including a drive spindle subjected to sudden deceleration under certain conditions of operation, a flywheel on said spindle rotatable relative thereto, a first disc on one side of said flywheel fixed on said spindle, a second disc on the other side of said flywheel axially movable on said spindle, cam means between said first disc and flywheel operatively associated with said second disc to impart axial movement thereto in one direction by virtue of a predetermined inertia of said flywheel upon said deceleration of said spindle, a valve controlling the supply of motive fluid to said motor, a spring normally urging and maintaining said valve in closed position, an operator for said valve movable relative thereto in valve open or closed positions, an operating connection between said operator and valve to open the valve upon movement of said operator to said valve open position, said operating connection including a lever and a crank member, said lever pivotally engaging said crank member, said operator engaging said lever for actuating said crank member, said connection capable of release to enable said valve to close by virtue of said spring even though said operator is in said valve open position, and means responsive to the axial movement of said second disc in said one direction to close said valve and interrupt said supply of motive fluid.

References Cited in the file of this patent UNITED STATES PATENTS 2,198,034 Farmer Apr. 23, 1940 2,384,399 Reynolds Sept. 4, 1945 2,675,713 Acker Apr. 20, 1954 2,717,672 Maurer Sept. 13, 1955 2,766,853 Trevashis et a1 Oct. 16, 1956 2,768,546 Amtsberg Oct. 30, 1956 2,775,327 Gearhart Dec. 25, 1956 FOREIGN PATENTS 1,120,566 France Apr. 23, 1956 569,901 Canada Feb. 3, 1959 

